# How do you find the indicated sum of a geometric series?

Calculate the vulgar connection of the succession. This is referred to as r. Your temporization to experience r depends on how ample you already perceive about the succession. If you perceive the primitive and remedy account, portio the remedy account by the primitive account to experience the vulgar connection.

it dominion be in any for if it is in a percentage relish a is 40 % of b

we perceive that their connection succeed be 4:10

Identify the primitive account in the succession. This is referred to as a. You may be potent to abundantly realize this account, but you may insufficiency to use other counsel you entertain to explain for the account.

If you don't perceive the primitive account in the succession, but you perceive the vulgar connection, the latest account and the reckon of accounts in the train you can experience the primitive account by solving for a in the aftercited equation:

latest account = a## (vulgar connection ^ ("n" accounts - 1)##)

or

##tn = ar^n - 1 ##

Solve for the sum. The sum is referred to as Sn. Insert your values into the aftercited equation:

sum of train = primitive account ( 1 - vulgar connection ^ reckon of accounts) / (1 - vulgar connection)

or

##S_n=a(1-r^n)÷(1-r)##

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